Is My Solar Power System Underperforming?

If you think your solar system isn’t working as well as it should, its wise to act fast.

When your system was first designed, the company you purchased it from should have provided an indication of how they expected your system to perform, and how they expected it might affect your power bills. If you’ve noticed a difference between this estimate and your system’s performance, it’s worth investigating further.

The top three indicators that your solar system might be underperforming:

  • Your bills aren’t as low as you expected or they’ve started to climb back up.

While your bills shouldn’t be the only place to look, they might be the first indicator that something’s not quite right. If you’re used to a certain figure coming in the post or via email each quarter, and this has recently changed, it’s definitely worth following up with either your electricity retailer or your solar retailer to see if there are any issues at the heart of it. As part of this, you should also review your own electricity usage patterns: have they changed, or is everything still the same as before? Any changes to your behaviour in terms of electricity use, for example, day-time vs night-time use, changes to appliance use, or a new air-conditioning system, might be the cause of the bill shock rather than any issues with your solar.

  • Your system’s output data doesn’t match the indication that you were given by your retailer or installer.

When you were given your system quote and design specifications, you should have also been provided some estimates as to the expected performance or output.  If these figures look drastically different, or you’re not sure they’re correct, don’t hesitate to call your installer to follow up with them. There could be a simple explanation – especially in the case of a newly installed system or inclement weather – but it’s always better to be proactive.

  • Your inverter’s display screen or system interface is showing an error.

This is the easiest way to detect something is wrong – but as solar inverters are often in “out of sight, out of mind” locations it’s often not checked by solar owners until it’s too late. Make it a routine to check your inverter for any errors regularly, and you’ll be sure to catch any issues before they spiral. If you’re a ZEN Energy customer, you will have been sent a user manual for your inverter/s with your ZEN Energy Welcome Pack or, for newer systems, you may even be able to find the relevant user manual in our Knowledge Centre.

How much power should my solar system be producing?

The Clean Energy Council has a set of guidelines for the design and installation of solar in Australia, which reputable solar companies and their installers must follow. Part of these guidelines set out the manner in which the energy generation for a solar system should be calculated, taking into consideration factors like where in Australia the system is, which way the panels face, the incline of the panels relative to the ground, and any shading on the panels (such as from trees or other nearby structures). For every kilowatt (kW) of solar that is installed on a completely north-facing roof, at an incline of 30 degrees and with no shading, the Clean Energy Council guidelines state that the average daily performance you can expect from your system over a full year should be as follows:

City Average daily output per kW of solar installed
Adelaide 4.2 kWh
Alice Springs 5.0 kWh
Brisbane 4.2 kWh
Cairns 4.2 kWh
Canberra 4.3 kWh
Darwin 4.4 kWh
Hobart 3.5 kWh
Melbourne 3.6 kWh
Perth 4.4 kWh
Sydney 3.9 kWh

Remember that this kWh figure is the expected daily output on average over a 12 month period – across all seasons, with a variety of weather conditions factored in. For example, in an Adelaide winter, with shorter days and often more cloud cover, the daily kWh output might be slightly lower, for example, 3 or 3.5 kWh per kW of solar installed. But, in spring or summer with lots of sunshine, it might be higher – up to 5 or even 6kWh.

Also remember that this is the expected output for a kilowatt of solar installed fully north facing, at an incline of 30 degrees, and with no shading: in “perfect conditions”. If your panels face east or west, are at a slightly different incline, or are subject to some shade, the performance will be lower.

Does this all seem confusing or difficult to apply and understand?

It might appear complex, but if you have access to some historical data for your system, or you received a detailed report of the expected performance of your system when it was first quoted, it should be pretty straightforward.

If you’re worried your system is underperforming, the simplest way to check is to review its recent daily average kilowatt-hour (kWh) output and compare it against what it has been producing before, or the estimates the solar company gave you at the time it was installed. Both of these comparisons are the easiest way to determine if your system is doing what it was expected to do, as it will have accounted for where your panels are, which direction(s) they face, their incline, and any shading. If the current performance of your system is markedly lower than it has been previously, or it’s very different to the installer’s estimates, it might be worth logging an enquiry with the installers.

How to maximise the efficiency of your solar system

  • Remove any areas of shading or covering

Shade is the solar panel’s number one enemy. Shading on just one panel, even intermittently or only at certain times of the day or year, can affect your overall system performance. Make sure you’re keeping on top of things like any new tree growth around your home, leaves falling onto your roof, or the placement of any new equipment like roof-mounted antennas or air-conditioning condensers.

Note – We don’t recommend climbing up a ladder for any DIY tree maintenance. If it’s not something you can address with both feet firmly planted on the ground, eliminate the risk of falls and call in a specialist contractor  – they’ve got the right tools and equipment to get the job done safely.

  • Make sure your solar panels are clean and free of debris

Anything that covers up the effective area of your solar panels will reduce their output. Similar to shade, debris or dirt can also be the cause of a decrease in performance. Usually, rain is enough to wash off dust and dirt on a regular basis, but sometimes, especially for stubborn bird droppings, damp leaves, or panels that aren’t installed on some sort of incline, the job might need a bit more elbow grease.

Note – Again, we don’t recommend you climb up onto your roof to clean your panels; climbing ladders and balancing on steep roofs can be dangerous. If possible, try to clean your panels from the safety of the ground using an extension handle on your squeegee or cloth and a bucket of water or your garden hose. If this isn’t feasible, call one of the many professional solar panel cleaning companies to help you out.

  • Maximise self-consumption and reduce your demand from the grid

Use as much of your free, solar-generated electricity during daylight hours as you can. Recharge devices, such as laptops, tablets and mobile phones during the day instead of overnight. Use your washing machine, clothes dryer or dishwasher during the day, so you can come home to clean clothes and clean dishes when you get home from work. Set your air conditioner to work during the day – either by a smartphone app or a timer – to pre-cool or pre-heat your home while you’re out during the day. Ideally, if your home has reached the perfect temperature by the early evening, you might be able to turn it off and reduce the amount of power you draw from the grid.

To take this even further, try to limit the number of electric appliances you’re using at one time. The size of your solar system will limit the amount of electricity that you can draw from it at once. Using two high-demand appliances at once might mean you’ll end up drawing from the grid for the excess required. For example, if you’re running the dishwasher, wait until it’s finished before starting up the washing machine or the clothes dryer.

Check out our guide ‘how to save money on your energy bills’ for more tips.